Nanocomposite polyurethane coating for aviation and preparation method therefor

Abstract

Provided are a nanocomposite polyurethane coating for aviation and a preparation method therefor. The coating is a product obtained by mixing a polyaspartic acid ester resin as a raw material with a fluorine-modified nano-SiO2 containing an active amine group and a fluorocarbon resin and reacting same. The nanocomposite polyurethane coating for aviation solves the problems of poor stain resistance, difficulty in cleaning, and poor toughness of existing aircraft skin coatings, and improves the toughness and ease of cleaning of the coating.

Description

A nanocomposite polyurethane coating for aviation and its preparation method Technical Field

[0001] The present invention relates to the technical field of functional coatings, and in particular to a nano composite polyurethane coating for aviation and a preparation method thereof. Background Art

[0002] During flight, aircraft often face rapid changes in temperature, strong impact and wear from high-speed airflow and airborne impurities, as well as frequent vibration and deformation of the wings. This requires aircraft skin coatings, especially long-lasting aircraft skin coatings, to have excellent resistance to temperature shock, low-temperature toughness, impact toughness, and wear resistance. Aircraft often fly long distances across regions. During flight, they are contaminated by dust in the atmospheric environment, exhaust particulate matter from fuel combustion, and fuel and hydraulic oil. This not only affects the appearance but also the service life of the aircraft skin. In recent years, driven by government environmental protection policies and the improvement of people's environmental awareness, environmentally friendly low-VOCs coatings have become a research hotspot in various coatings fields. Currently, the main domestic aircraft skin coatings include acrylic polyurethane coatings, polyester polyurethane coatings, fluorocarbon polyurethane coatings, and silicone-modified polyurethane coatings. The above-mentioned types of skin coatings each have their own characteristics. Acrylic polyurethane coatings and polyester polyurethane coatings can both be used to prepare high-solids environmentally friendly coatings, but acrylic polyurethane coatings have poor flexibility. Although polyester polyurethane coatings have good toughness, their paint film hardness is low and their stain resistance is poor. Fluorocarbon polyurethane coatings and silicone-modified polyurethane coatings have good stain resistance and wear resistance, but due to the influence of resin, it is difficult to prepare high-solids coatings for both, and their flexibility is poor.

[0003] Chinese invention patent application CN102220071A discloses a high-solids aircraft skin coating with VOCs <420 g / L, but does not address research on the coating's flexibility or cleanability. Patent CN 109021803 A discloses a varnish for aircraft skin that combines excellent weather resistance and toughness, and its preparation method. The coating exhibits excellent thermal shock resistance and weather resistance (93% gloss retention after 1500 hours of artificial aging), but no data on low-temperature flexibility, impact flexibility, or cleanability is reported. Chinese invention patent application CN116218343 A discloses a stain-resistant matte polyurethane coating for skin. This technology addresses the poor stain resistance of matte polyurethane coatings while also exhibiting excellent weather resistance. However, no data on the coating's flexibility is reported, and the VOC content is high. Therefore, there is an urgent need to improve the thermal shock resistance, low-temperature flexibility, and impact toughness of aircraft skin coatings. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the purpose of this application is to provide a nano-composite polyurethane coating for aviation, to solve the problems of poor stain resistance, difficulty in cleaning and poor toughness of existing aircraft skin coatings, and to improve the toughness and easy cleaning properties of the coating.

[0005] To solve the above problems, the technical solutions adopted in this application are as follows:

[0006] The embodiment of the present application provides a nano-composite polyurethane coating for aviation, which is a product obtained by mixing polyaspartic acid ester resin as a raw material with fluorine-modified nano-SiO2 and fluorocarbon resin.

[0007] As a further and preferred solution, the nanocomposite polyurethane coating for aviation described in the embodiment of the present application comprises component A and component B, wherein

[0008] The A component comprises the following components in weight percentage:

[0009] Polyaspartic acid resin 20%-28%,

[0010] Fluorocarbon resin 15%-25%,

[0011] Fluorine-modified nano-SiO2 particles 1%-3%,

[0012] Additives 2%-5%,

[0013] Pigment 25%-35%,

[0014] Filler 10%-15%,

[0015] Matting powder 3%-5%,

[0016] Mixed solvent 6%-10%;

[0017] The B component comprises the following components by weight percentage:

[0018] HDI biuret 44%-47%,

[0019] HDI trimer 50%-56%,

[0020] Dehydrating agent 1-2%;

[0021] The addition amount of component B is 15wt%-25wt% of component A.

[0022] As a further and preferred solution, the polyaspartic acid ester resin described in the embodiment of the present application contains both flexible and rigid structures, and is prepared by addition polymerization of maleate and primary diamine.

[0023] As a further and preferred solution, the polyaspartic acid ester resin described in the examples of the present application has a relative molecular weight of 500-800 and a viscosity of 1200-1500 mPa·s.

[0024] As a further and preferred solution, the fluorine content of the fluorocarbon resin described in the embodiments of the present application is ≥26%, and the viscosity is 2000-3500 mPa·s.

[0025] As a further and preferred embodiment, the additives described in the embodiment of the present application include one or more of a defoaming agent, a leveling agent, a dispersant, an anti-settling agent, and an ultraviolet absorber; the filler is one or more of precipitated barium sulfate, mica powder, talc powder, silica powder, and feldspar powder; and the mixed solvent is a mixture of any two or more of xylene, butyl acetate, propylene glycol methyl ether acetate, methyl isobutyl ketone, and methyl ethyl ketone.

[0026] As a further and preferred solution, the modified nano-SiO2 particles described in the embodiment of the present application are prepared by in-situ modification using a sol-gel method, and the preparation method is as follows:

[0027] Hydrolysis: Disperse the silicate in a solvent, add a catalyst solution and stir to mix evenly, and slowly dropwise add deionized water under stirring to carry out a hydrolysis reaction to obtain a reaction solution;

[0028] Coupling modification: adding a fluoroalkylsilane coupling agent and an aminosilane coupling agent to the above reaction solution, stirring evenly, adding deionized water during the stirring process, heating to the reaction temperature until the reaction is complete, and obtaining a uniform and transparent sol;

[0029] Centrifugation and filtration: The above sol is centrifuged and filtered to obtain SiO2 gel, which is then repeatedly washed and centrifuged at least twice, and then dried to obtain fluorine-modified nano-SiO2 particles.

[0030] As a further and preferred solution, in the preparation of fluorine-modified nano-SiO2 particles described in the embodiments of the present application, the mass ratio of catalyst, silicate, fluoroalkyl silane coupling agent and aminosilane coupling agent is 3: (8-12): (3-7): (3-7).

[0031] As a further and preferred embodiment, the silicate described in the embodiment of the present application is one or more of methyl silicate, ethyl silicate, propyl silicate, and butyl silicate; the fluoroalkyl silane coupling agent is one or more of perfluorodecyltrimethoxysilane, perfluorodecyltriethoxysilane, perfluorooctylmethyldimethoxysilane, and perfluorooctyltriethoxysilane.

[0032] The present invention also provides a method for preparing a nano-composite polyurethane coating for aviation, comprising:

[0033] Preparation of coating paste: Add polyaspartic acid ester resin, a portion of mixed solvent, dispersant and defoamer into a dispersion tank, stir and mix evenly, add anti-settling agent, fluorine-modified nano-SiO2 particles, pigment and filler, stir and mix evenly at high speed, grind and disperse, filter and discharge to obtain nano-composite polyurethane coating paste;

[0034] Preparation of component A: Add the above-mentioned nano-composite polyurethane coating color paste, fluorocarbon resin, silane coupling agent, additives, and the remaining mixed solvent into a dispersion tank and stir and mix them evenly to obtain component A;

[0035] Preparation of component B: Add HDI biuret, HDI trimer and dehydrating agent into a dispersion tank, stir and mix evenly to obtain component B;

[0036] Preparation of aviation nano-composite polyurethane coating: Mix the above-mentioned component A and component B, add an appropriate amount of solvent to dilute, and stir and mix evenly to obtain the aviation nano-composite polyurethane coating.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The aviation nano-composite polyurethane coating described in this application uses polyaspartic acid resin as a raw material and fluorine-modified nano-SiO2 and fluorocarbon resin as raw materials. During the coating curing process, the fluorocarbon structure of the nano-SiO2 pulls it to migrate to the coating surface, forming an organic / inorganic hybrid micro-nano rough structure composed of fluorocarbon structure, SiO2 particles, fluorocarbon resin and resin, constructing a hydrophobic and oleophobic anti-fouling surface. Inside the coating, a network structure of interpenetrating nano-SiO2, fluorocarbon resin and polyaspartic acid resin is formed, which makes the aviation nano-composite polyurethane coating easy to clean.

[0039] 2. The aviation nanocomposite polyurethane coating described in this application has active amine groups. The network structure formed during the curing process is beneficial to improving the strength and wear resistance of the micro-nanostructure on the coating surface, avoiding the disadvantage of poor long-term anti-fouling ability of the coating caused by insufficient wear resistance of traditional micro-nanostructures.

[0040] 3. The polyaspartic acid ester resin used in the aviation nano-composite polyurethane coating described in this application has excellent flexibility, wear resistance, and weather resistance. The addition of fluorocarbon resin improves the coating strength, heat deformation temperature, and chemical resistance without affecting the toughness of the coating, which is beneficial to improving the coating's resistance to temperature shock.

[0041] The present invention will be further described in detail below with reference to specific embodiments. DETAILED DESCRIPTION

[0042] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0043] The term "comprising" and other equivalent descriptions in the description and claims of this application are intended to cover non-exclusive inclusions, including both the contents clearly described in the description and claims and the steps or units that are not described in the description and claims but are inherent in the product, method or structure.

[0044] The present application provides a nano-composite polyurethane coating for aviation, which is a product obtained by reacting polyaspartic acid ester resin with fluorine-modified nano-SiO2 and fluorocarbon resin. The specific aviation nano-composite polyurethane coating described in the present application includes component A and component B; wherein component A contains the following components by weight percentage: 20%-28% polyaspartic acid ester resin, 15%-25% fluorocarbon resin, 1%-3% fluorine-modified nano-SiO2 particles, 2%-5% additive, 25%-35% pigment, 10%-15% filler, 3%-5% matting agent, and 6%-10% mixed solvent; and component B contains the following components by weight percentage: 44%-47% HDI biuret, 50%-56% HDI trimer, and 1-2% dehydrating agent; and the amount of component B added is 15wt%-25wt% of component A.

[0045] In the above scheme, during the curing process of the aviation nano-composite polyurethane coating described in the embodiment of the present application, the fluorocarbon structure in the fluorine-modified nano-SiO2 particles pulls them to the coating surface, forming an organic / inorganic hybrid micro-nano rough structure composed of fluorocarbon structure, SiO2 particles, fluorocarbon resin and polyaspartic acid ester resin on the coating surface, constructing a hydrophobic and oleophobic anti-fouling surface, which coordinates with the network structure formed by nano-SiO2, fluorocarbon resin and polyaspartic acid ester resin in the coating, giving the aviation nano-composite polyurethane coating easy cleaning properties.

[0046] Compared with acrylic resin, polyaspartic acid resin has excellent flexibility, wear resistance and weather resistance. In the embodiment of the present application, polyaspartic acid resin is used as the main resin raw material of component A, and HDI biuret and HDI trimer in component B are both flexible curing agents. After components A and B are mixed, the polyaspartic acid resin interacts with the flexible HDI biuret and flexible HDI trimer curing agents, and the resulting cured coating has excellent impact resistance, impact toughness and low-temperature toughness. The addition of fluorocarbon resin can effectively improve the coating strength, heat deformation temperature and chemical resistance, as well as improve the temperature shock resistance of the coating without affecting the toughness of the coating.

[0047] Preferably, in some embodiments of the present application, the polyaspartic acid ester resin comprises both flexible and rigid structures and is produced by the addition polymerization of maleic acid esters and primary diamines. The viscosity of the polyaspartic acid ester resin affects the solid content of the coating and the mechanical properties of the coating. To achieve a high-solids, low-VOC coating product, the polyaspartic acid ester resin described in the embodiments of the present application has a relative molecular weight of 500-800 and a viscosity of 1200-1500 mPa·s.

[0048] Due to the high electronegativity of fluorine atoms, the carbon-fluorine bond energy of the C-F bond in fluorocarbon resins is relatively strong. The C-F bond helically wraps around the low-energy C-C bond, providing excellent shielding and protection, effectively blocking the damaging effects of ultraviolet rays. The higher the fluorine content of the fluorocarbon resin in the aviation nanocomposite polyurethane coating described herein, the better the gloss and color retention of the resulting coating. Increasing the fluorine content significantly improves the coating's resistance under experimental testing conditions. Therefore, to achieve a coating with excellent aging resistance and ease of cleaning, in some preferred embodiments, the fluorine content of the fluorocarbon resin is ≥26% and the viscosity is 2000-3500 mPa·s.

[0049] As a further and preferred embodiment, in some embodiments of the present application, the additives used include one or more of defoamers, leveling agents, dispersants, anti-settling agents, and UV absorbers. The filler is preferably an inorganic filler and can be selected from, but not limited to, one or more of inorganic powders such as precipitated barium sulfate, mica powder, talc, silica powder, and feldspar powder. The mixed solvent is a mixture of any two or more of xylene, butyl acetate, propylene glycol methyl ether acetate, methyl isobutyl ketone, and methyl ethyl ketone. In some embodiments of the present application, the pigment used is a coloring pigment selected from, or a mixture of two or more of, yellow iron oxide, red iron oxide, rutile titanium dioxide, and carbon black.

[0050] In the examples of the present application, the fluorocarbon structure in the fluorine-modified nano-SiO2 particles has a significant impact on the performance of the coating. Preferably, in some embodiments, the fluorine-modified nano-SiO2 particles are in-situ modified by the sol-gel method, and the preparation method is as follows:

[0051] Hydrolysis: Disperse the silicate in a solvent, add a catalyst solution and stir to mix evenly, and slowly dropwise add deionized water under stirring to carry out a hydrolysis reaction to obtain a reaction solution;

[0052] Coupling modification: adding a fluoroalkylsilane coupling agent and an aminosilane coupling agent to the above reaction solution, stirring evenly, adding deionized water during the stirring process, heating to the reaction temperature until the reaction is complete, and obtaining a uniform and transparent sol;

[0053] Centrifugation and filtration: The above sol is centrifuged and filtered to obtain SiO2 gel, which is then repeatedly washed and centrifuged at least twice, and then dried to obtain fluorine-modified nano-SiO2 particles.

[0054] As a further and preferred embodiment, in the preparation of fluorine-modified nano-SiO2 particles described in the examples of this application, the mass ratio of the catalyst, silicate, fluoroalkyl silane coupling agent, and aminosilane coupling agent is 3:(8-12):(3-7):(3-7). In a preferred embodiment, the mass ratio of the catalyst, silicate, fluoroalkyl silane coupling agent, and aminosilane coupling agent is 3:10:5:5. The addition of the fluoroalkyl silane coupling agent and aminosilane coupling agent in equal mass ratios facilitates the successful grafting of two silane structures onto the SiO2 surface, effectively preventing some nanoparticles from being grafted with only one silane.

[0055] The fluorine-modified nano-SiO2 particles in situ modified by the sol-gel method have a large number of fluorocarbon structures on their surface, which can change the structure of the coating surface. The fluorine-modified nano-SiO2 particles contain active amine groups. During the coating curing process, they react with the curing agent to form a network structure. On the one hand, they can improve the strength and wear resistance of the micro-nano structure on the coating surface, avoiding the shortcoming of poor long-term anti-fouling ability of the coating caused by insufficient wear resistance of traditional micro-nano structures; on the other hand, when the coating is impacted, the nano-SiO2 particles in the microstructure produce silver streaks to absorb external forces, prevent the generation of cracks in the coating, and synergize with the flexible polyaspartic acid resin to improve the coating's resistance to cracking.

[0056] Specifically, in some embodiments of the present application, the silicate ester used is one or more of methyl silicate, ethyl silicate, propyl silicate, and butyl silicate. The fluoroalkyl silane coupling agent is one or more of perfluorodecyltrimethoxysilane, perfluorodecyltriethoxysilane, perfluorooctylmethyldimethoxysilane, and perfluorooctyltriethoxysilane. The catalyst is one or more of glacial acetic acid, hydrochloric acid, and ammonia solution.

[0057] Preferably, during the preparation of the fluorine-modified nano-SiO2 particles, the hydrolysis temperature does not exceed 40°C. During the coupling modification process, the reaction temperature is 55°C-65°C, preferably 60°C, and the stirring time is 5-8 hours, preferably 6 hours. The drying is carried out at a constant temperature of 80°C for 15-20 hours.

[0058] The present invention also provides a method for preparing a nano-composite polyurethane coating for aviation, comprising:

[0059] Preparation of coating paste: Add polyaspartic acid ester resin, a portion of mixed solvent, dispersant and defoamer into a dispersion tank, stir and mix evenly, add anti-settling agent, fluorine-modified nano-SiO2 particles, pigment and filler, stir and mix evenly at high speed, grind and disperse, filter and discharge to obtain nano-composite polyurethane coating paste;

[0060] Preparation of component A: Add the above-mentioned nano-composite polyurethane coating color paste, fluorocarbon resin, silane coupling agent, additives, and the remaining mixed solvent into a dispersion tank and stir and mix them evenly to obtain component A;

[0061] Preparation of component B: Add HDI biuret, HDI trimer and dehydrating agent into a dispersion tank, stir and mix evenly to obtain component B;

[0062] Preparation of aviation nano-composite polyurethane coating: Mix the above-mentioned component A and component B, add an appropriate amount of solvent to dilute, and stir and mix evenly to obtain the aviation nano-composite polyurethane coating.

[0063] The following are specific examples of the present application. In the following examples, the raw materials used include: polyaspartic acid ester resin (Desmophen NH 1520, Covestro), fluorocarbon resin (ETERFLON 41070, Changxing), anti-settling agent (BYK410, BYK), defoaming agent (BYK 066N, BYK), fluorine-modified nano-SiO2 particles, titanium dioxide (R706, Chemours), carbon black (MA100, Mitsubishi), iron yellow (YZ1688 Pannengtuo), matting agent (ED30, Grace), leveling agent (AFCONA 3777, BASF), UV absorber (Tinuvin400, BASF), light stabilizer (Tinuvin123, BASF), HDI biuret (N75, Covestro), HDI trimer (N3800, Covestro), and dehydrating agent (OF, Bayer).

[0064] Example 1

[0065] This embodiment provides a fluorine-modified nano-SiO2 particle, which is prepared by in-situ modification using a sol-gel method. The preparation method is as follows:

[0066] Hydrolysis: Disperse 10 g of ethyl silicate in 40 g of ethanol, add 3 g of glacial acetic acid solution and stir to mix evenly, then slowly add deionized water dropwise while stirring and hydrolyze at 40°C for 2 h to obtain a reaction solution;

[0067] Coupling modification: Add 5g of perfluorooctyltriethoxysilane coupling agent and 5g of aminosilane coupling agent AMEO (Degussa) to the above reaction solution and stir evenly. Add deionized water during stirring, raise the temperature to 60°C and continue stirring for 6h to obtain a uniform and transparent sol.

[0068] Centrifugation and filtration: The above sol is centrifuged and filtered to obtain SiO2 gel, which is repeatedly washed and centrifuged three times with anhydrous ethanol, and then dried at a constant temperature of 80°C to obtain fluorine-modified nano-SiO2 particles.

[0069] Example 2

[0070] This embodiment provides an aviation nano-composite polyurethane coating, and the mass percentage of each component is shown in Table 1.

[0071] Table 1

[0072]

[0073] The preparation method of the high-toughness, easy-to-clean, high-solid-content aviation nanocomposite polyurethane coating of this embodiment is as follows:

[0074] (1) Add the formulated amount of polyaspartic acid ester resin, part of the mixed solvent, dispersant, defoamer and anti-settling agent to a dispersion tank, stir at a speed of 500 rpm for 15 minutes to mix evenly, add the fluorine-modified nano-SiO2 particles obtained in Example 1 under stirring, disperse at a speed of 1200 rpm for 20 minutes, and after complete mixing, add titanium dioxide, barium sulfate, feldspar powder, carbon black and iron yellow in sequence at a speed of 800 rpm. After the addition is completed, increase the speed to 1500 rpm and disperse for 20 minutes, then add zirconium beads and grind and disperse for 3 hours. When the slurry fineness is ≤5 μm, filter the material to obtain the aviation nano-composite polyurethane coating color paste;

[0075] (2) The aviation nanocomposite polyurethane coating color paste prepared in the above steps was added to a dispersion tank, and then fluorocarbon resin, matting agent, ultraviolet light absorber, light stabilizer, leveling agent and the remaining mixed solvent were added in sequence under stirring at 800 rpm, and the speed was increased to 1200 rpm and dispersed for 20 minutes to obtain component A;

[0076] (3) Add HDI biuret, HDI trimer and dehydrating agent into the dispersion tank, stir and mix evenly to obtain component B;

[0077] (4) Mix the above components A and B, add an appropriate amount of solvent to dilute, and stir to mix evenly to obtain the aviation nano-composite polyurethane coating.

[0078] Example 3

[0079] This embodiment provides an aviation nanocomposite polyurethane coating, the mass percentages of the components are shown in Table 2:

[0080] Table 2

[0081]

[0082] The preparation method of the aviation nanocomposite polyurethane coating described in this embodiment is as follows:

[0083] (1) Add the formulated amount of polyaspartic acid ester resin, part of the mixed solvent, dispersant, defoamer and anti-settling agent into the dispersion tank, stir at 500 rpm for 15 min to mix evenly, add fluorine-modified nano-SiO2 particles while stirring, disperse at 1200 rpm for 20 min, and after complete mixing, add titanium dioxide, barium sulfate, feldspar powder, carbon black and iron yellow in sequence at 800 rpm. After the addition is completed, increase the speed to 1500 rpm and disperse for 20 min, then add zirconium beads and grind and disperse for 3 h. When the slurry fineness is ≤5 μm, filter the material to obtain a high-toughness, easy-to-clean, high-solid-content aviation nano-composite polyurethane coating color paste;

[0084] (2) The high-toughness, easy-to-clean, high-solid-content aviation nano-composite polyurethane coating color paste prepared in the above steps was added to a dispersion tank, and then fluorocarbon resin, matting powder, ultraviolet light absorber, light stabilizer, leveling agent and the remaining mixed solvent were added in sequence under stirring at 800 rpm, and the speed was increased to 1200 rpm for dispersion for 20 minutes to obtain component A;

[0085] (3) Add HDI biuret, HDI trimer and dehydrating agent into the dispersion tank, stir and mix evenly to obtain component B;

[0086] (4) Mix the above components A and B, add an appropriate amount of solvent to dilute, and stir to mix evenly to obtain the aviation nano-composite polyurethane coating.

[0087] Comparative Example 1

[0088] This comparative example provides an aviation nanocomposite polyurethane coating, which uses hydroxyl acrylic resin as the resin raw material. The mass percentages of the components are shown in Table 3:

[0089] Table 3

[0090]

[0091] The preparation method of the aviation nano-composite polyurethane coating is as follows:

[0092] (1) Add the formulated amount of hydroxy acrylic resin, part of the mixed solvent, dispersant, defoamer and anti-settling agent into the dispersion tank, stir at 500 rpm for 15 min to mix evenly, add fluorine-modified nano-SiO2 particles while stirring, disperse at 1200 rpm for 20 min, and after complete mixing, add titanium dioxide, barium sulfate, feldspar powder, carbon black and iron yellow in sequence at 800 rpm. After the addition is completed, increase the speed to 1500 rpm and disperse for 20 min, then add zirconium beads and grind and disperse for 3 h. When the slurry fineness is ≤5 μm, filter the material to obtain a high-toughness, easy-to-clean, high-solid-content aviation nano-composite polyurethane coating color paste;

[0093] (2) The high-toughness, easy-to-clean, high-solid-content aviation nano-composite polyurethane coating color paste prepared in the above steps was added to a dispersion tank, and then fluorocarbon resin, matting powder, ultraviolet light absorber, light stabilizer, leveling agent and the remaining mixed solvent were added in sequence under stirring at 800 rpm, and the speed was increased to 1200 rpm for dispersion for 20 minutes to obtain component A;

[0094] (3) Add HDI biuret, HDI trimer and dehydrating agent into the dispersion tank, stir and mix evenly to obtain component B;

[0095] (4) Mix the above components A and B, add an appropriate amount of solvent to dilute, and stir to mix evenly to obtain the aviation nano-composite polyurethane coating.

[0096] Comparative Example 2

[0097] This comparative example provides an aviation nano-composite polyurethane coating. The difference from Examples 2-4 is that no fluorine-modified nano-SiO2 particles are added, and hydroxyl acrylic resin is used as the resin raw material. The mass percentages of the components are shown in Table 4.

[0098] Table 4

[0099]

[0100] The preparation method of the aviation nanocomposite polyurethane coating described in this comparative example is as follows:

[0101] (1) Add the formulated amount of hydroxy acrylic resin, part of the mixed solvent, dispersant, defoamer and anti-settling agent into the dispersion tank, stir at 500 rpm for 15 min to mix evenly, add fumed silica while stirring, disperse at 1200 rpm for 20 min, and after completely mixing, add titanium dioxide, barium sulfate, feldspar powder, carbon black and iron yellow in sequence at 800 rpm. After the addition is completed, increase the speed to 1500 rpm and disperse for 20 min, then add zirconium beads and grind and disperse for 3 h. When the slurry fineness is ≤5 μm, filter the material to obtain a high-toughness, easy-to-clean, high-solid-content aviation nano-composite polyurethane coating color paste;

[0102] (2) The high-toughness, easy-to-clean, high-solid-content aviation nano-composite polyurethane coating paste prepared in the above steps was added to a dispersion tank, and then matting powder, ultraviolet light absorber, light stabilizer, leveling agent and the remaining mixed solvent were added in sequence under stirring at 800 rpm, and the speed was increased to 1200 rpm for dispersion for 20 minutes to obtain component A;

[0103] (3) Add HDI biuret, HDI trimer and dehydrating agent into the dispersion tank, stir and mix evenly to obtain component B;

[0104] (4) Mix the above components A and B, add an appropriate amount of solvent to dilute, and stir to mix evenly to obtain the aviation nano-composite polyurethane coating.

[0105] The polyurethane coatings prepared in Examples 2-3 and Comparative Examples 1-2 were subjected to performance tests. The test substrate used was an anodized 2A12 aluminum alloy plate having a size of 0.5 mm × 70 mm × 150 mm. The test results are shown in Table 5. The test method and process are described as follows:

[0106] (1) Low temperature flexibility

[0107] The low-temperature flexibility of the polyurethane coating prepared in the present invention is tested in accordance with the provisions of GB / T 6742. The test environment temperature is (-51±3)°C, and the test is performed using a type II bending tester with a cylindrical shaft diameter of 20 mm and a 10x magnifying glass.

[0108] (2) Impact flexibility

[0109] The impact flexibility of the polyurethane coating prepared in the present invention is tested in accordance with the provisions of ASTM D6905. Observation is performed using a 10x magnifying glass, and the maximum elongation at which no cracks occur in the test coating is recorded.

[0110] (3) Temperature shock resistance

[0111] The polyurethane coating prepared in this invention was tested for thermal shock resistance according to GJB 150.5A. The low-temperature test temperature was (-55 ± 5)°C for 1 hour, and the high-temperature test temperature was (70 ± 5)°C for 1 hour. The transition time between high and low temperatures was no longer than 1 minute, and one low-temperature test and one high-temperature test constituted a single cycle.

[0112] (4) Impact resistance

[0113] The impact resistance of the polyurethane coating prepared in the present invention is tested in accordance with the provisions of GB / T 1732. The maximum impact height at which no cracking or falling off occurs is recorded.

[0114] (5) Wear resistance

[0115] The wear resistance of the polyurethane coating prepared in the present invention is tested according to the provisions of GB / T 1768, CS10, 1000g / 1000r, and the abrasion loss is recorded.

[0116] (6) Easy to clean

[0117] The cleanability of the polyurethane coating prepared in the present invention was tested according to the method specified in 4.6.13 of the military standard MIL-PRF-85285D, and the cleaning rate was calculated.

[0118] (7) Artificially accelerated aging

[0119] The artificial accelerated aging test of the polyurethane coating prepared by the present invention is carried out according to the provisions of GB / T 1865, 3000 hours, UVB-313, 4 hours of drying, 4 hours of condensation, and the test color difference and gloss loss rate are recorded.

[0120] See Table 5 for test results.

[0121] Table 5

[0122]

[0123] The test results of Examples 2-3 and comparative examples above show that the addition of fluorine-modified nano-SiO2 particles can significantly improve the cleanability and wear resistance of the coating, and can improve the impact resistance and impact flexibility of the coating; the addition of polyaspartic acid ester resin can significantly improve the weather resistance of the coating, improve the impact flexibility, low-temperature flexibility and impact resistance of the coating, and synergize with the fluorine-modified nano-SiO2 particles to further improve the wear resistance of the coating. The high-toughness, easy-to-clean, high-solid content aviation nano-composite polyurethane coating prepared by the present invention has excellent environmental adaptability and can meet the protection and decoration requirements of aircraft skins in more severe environments.

[0124] The components listed in the present invention, as well as the upper and lower limits and intervals of the components of the present invention, can all achieve the present invention, and embodiments are not listed here one by one. The above lists some specific embodiments to illustrate the present invention. It is necessary to point out that the above and below specific embodiments are only used to further illustrate the present invention and do not represent a limitation on the scope of protection of the present invention.

Claims

1. A nano-composite polyurethane coating for aviation, characterized in that, It is a product obtained by mixing and reacting a polyaspartate resin as a raw material with fluorine-modified nano-SiO 2 and a fluorocarbon resin containing active amine groups.

2. The nano-composite polyurethane coating for aviation according to claim 1, characterized in that, it comprises component A and component B, wherein component A contains the following components by weight percentage: polyaspartic ester resin 20% - 28%, fluorocarbon resin 15% - 25%, Fluorine-modified nano-SiO 2 particles 1%-3%, auxiliary agent 2% - 5%, pigment 25% - 35%, filler 10% - 15%, matting powder 3% - 5%, mixed solvent 6% - 10%; component B contains the following components by weight percentage: HDI biuret 43% - 47%, HDI trimer 50% - 56%, dehydrating agent 1% - 2%; The addition amount of component B is 15wt% - 25wt% of component A.

3. The nano-composite polyurethane coating for aviation according to claim 2, characterized in that, the polyaspartic ester resin contains both flexible and rigid structures and is made by addition polymerization of maleic ester and primary diamine.

4. The nano-composite polyurethane coating for aviation according to claim 3, characterized in that, the relative molecular weight of the polyaspartic ester resin is 500 - 800, and the viscosity is 1200 - 1500 mPa·s.

5. The nano-composite polyurethane coating for aviation according to claim 2, characterized in that, the fluorine content of the fluorocarbon resin ≥ 26%, and the viscosity is 2000 - 3500 mPa·s.

6. The nano-composite polyurethane coating for aviation according to claim 2, characterized in that, the auxiliary agent includes one or more of defoamer, leveling agent, dispersant, anti-settling agent, ultraviolet absorber; the filler is one or more of precipitated barium sulfate, mica powder, talc powder, silica powder and feldspar powder; the mixed solvent is any two mixtures or three or more mixtures of xylene, butyl acetate, propylene glycol methyl ether acetate, methyl isobutyl ketone, methyl ethyl ketone.

7. The nano-composite polyurethane coating for aviation according to any one of claims 1 - 6, characterized in that, The modified nano-SiO 2 particles are in-situ modified by the sol-gel method, and the preparation method is as follows: Hydrolysis: Disperse the silicate ester in the solvent, add the catalyst solution and stir to make it uniformly mixed, and slowly dropwise add deionized water under stirring for hydrolysis reaction to obtain a reaction solution; Coupling modification: Add a fluoroalkylsilane coupling agent and an aminosilane coupling agent to the above reaction solution, stir evenly, add deionized water during the stirring process, heat up to the reaction temperature until the reaction is complete to obtain a uniformly transparent sol; Centrifugation and filtration: After centrifuging and filtering the above-mentioned sol, SiO 2 gel is obtained. Then, the SiO 2 gel is washed and centrifuged repeatedly at least twice, and after drying, fluorine-modified nano-SiO 2 particles are obtained.

8. The nano-composite polyurethane coating for aviation according to claim 7, characterized in that, The fluorine-modified nano-SiO 2 In the preparation of the particles, the mass ratio of the catalyst, silicate ester, fluoroalkylsilane coupling agent and aminosilane coupling agent is 3:(8-12):(3-7):(3-7).

9. The nano-composite polyurethane coating for aviation according to claim 7, characterized in that, the silicate ester is one or more of methyl silicate, ethyl silicate, propyl silicate, butyl silicate; the fluoroalkylsilane coupling agent is one or more of perfluorodecyltrimethoxysilane, perfluorodecyltriethoxysilane, perfluorooctylmethyldimethoxysilane, perfluorooctyltriethoxysilane.

10. A preparation method of a nano-composite polyurethane coating for aviation, characterized by comprising Preparation of coating color paste: Add polyaspartic ester resin, a partial amount of mixed solvent, dispersant and defoamer into a dispersion tank, stir and mix evenly, add anti-settling agent, fluorine-modified nano-SiO 2 particles, pigments and fillers. After high-speed stirring and mixing evenly, carry out grinding and dispersion, then filter and discharge to obtain nano-composite polyurethane coating color paste; Preparation of Component A: Add the above-mentioned nano-composite polyurethane coating color paste, fluorocarbon resin, silane coupling agent, additives, and the remaining mixed solvent into a dispersion tank, and stir and mix evenly to obtain Component A; Preparation of Component B: Add HDI biuret, HDI trimer, and dehydrating agent into a dispersion tank, and stir and mix evenly to obtain Component B; Preparation of aviation nano-composite polyurethane coating: Mix the above-mentioned Component A and Component B, dilute with an appropriate amount of solvent, and stir and mix evenly to obtain the aviation nano-composite polyurethane coating.

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